Electric iron and safety device therefor



Jan. 27, 1970 A. SCHWARTZ 3,492,459

ELECTRIC IRON AND SAFETY DEVICE THEREFOR 1 Filed Dec. 30, 1966 2 Sheets-Sheet l Filed Dec. 50, 1966 Jan. 27, 1970' A, SCHWARTZ 3,492,459

ELECTRIC IRON AND SAFETY DEVICE THEREFOR 2 Sheets-Sheet 2 fine I06 "Cg/I08 INVENTOR United States Patent US. Cl. 219-251 7 Claims ABSTRACT OF THE DISCLOSURE An electric iron having means for connecting the heating load to a source of electrical potential. A bidirectional gated semiconductive element included in the connecting means for interrupting the connecting means after a predetermined time delay.

CROSS-REFERENCE This invention relates to a safety shut-off device for manually operated electrically heated instruments or appliances and is an improvement over application Ser. No. 501,942, filed Oct. 22, 1965.

BACKGROUND AND OBJECTS Since heating instruments are used for a limited period of time and subsequently are left unattended, there is a possibility that the user will fail to turn-off the electric current to the unit. This presents a fire hazard, particularly where such units are left near or in contact with combustible materials.

A particular example of such a unit is the ordinary electric heating iron used in the home. The hazard of fire may be encountered in this instance where the housewife leaves her iron after use without turning it olf.

In these instances the iron may be left for many hours and may result in the ironing board and room catching fire. This potentially dangerous condition has been recognized, and many electrical cut-off switch devices have been proposed. However, none of the previous switch devices have been used successfully in the standard iron because of drawbacks in operation which made it inconvenient and annoying to the user of the iron.

The present invention is directed to an electrical cutoff switch arrangement which is not inconvenient to the user, and is automatically operated only when the iron has been left on by the user. It employs a time delay electric cut-off switch system which operates only after the heating instrument has been in an inactive position for a given period of time.

Accordingly, it is a principal object of this invention to provide a safety device for electrical heating appliances to eliminate the fire hazard created by unattended units which have not been turned-off after use.

Another important object is to provide a circuit cutoff which will prevent the unnecessary waste of electric current when an iron is left on unintentionally. Since present day electric irons are rated at about 1100 watts, an unattended iron could waste power equivalent to leaving on ten to fifteen lamps. Therefore, the invention provides an obvious saving in electricity costs.

It is another object to provide a safety cut-off switch which is very simple, compact and economically adapt able to the currently designed electric irons.

A further object is to provide a safety device to automatically cut-off an electric iron after a predetermined time delay which includes means on the handle which will not interfere with the operators use of the iron or require any attention or undue effort.

Further, the invention provides a device having a button on the handle to operate a time delay switch. This lCC button will call attention to the safety feature and provide sales appeal for the iron.

It is still a further object of this invention to provide an electrical cut-off circuit for an electrically operated heating appliance which will operate only after the appliance has been in use and has been left on by the user.

It is a further object of this invention to use the stored inactive position of a heating appliance as a means of activating a safety electrical cut-off switch assembly.

Another object of this invention is to provide a time delay electrical cut-off switch circuit for a heating appliance after the appliance has been used for a small period of time.

A still further object of this invention is to provide a circuit operating switch assembly in an appliance which will operate automatically without requiring a special action on the part of the user.

Another object of this invention is to provide an automatic safety circuit interrupter for the electric iron used in the home.

A still further object of this invention is to use a simple, compact cut-off switch assembly which can readily be used with standard manufactured heating appliances without requiring extensive modification thereof.

Yet a further object of this invention is to provide a cut-off switch assembly which is initially activated by a contact button which is depressed when the appliance is placed in an inactive, stored position.

A still further object of this invention is to provide a time delay circuit breaking switch assembly in the heating element circuit which is activated by movement of the heating unit to a stored, inactive position.

A still further object of the invention is to provide a bidirectional triode semiconductive (triac) element in series with the heating element, the time delay switch being located in the gate circuit of the triac.

SUMMARY This invention includes means for providing a time delay circuit interrupting switch assembly which opens a bidirectional semiconductive element in the heater circuit of a heating instrument a short time after the instrument is placed in a stored, inactive position, but which will instantly close such circuit when the instrument is moved from the stored, inactive position.

BRIEF DESCRIPTION OF THE DRAWINGS The subject matter of the invention is particularly pointed out and distinctly claimed in the concluding portion of this specification.

The invention, however, both as to organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanyings drawings in which:

FIGURE 1 is a side elevation view of the iron in its operating position;

FIGURE 2 is a view similar to FIGURE 1 of the iron in its rest position;

FIGURES 3 and 4 are section views of a switch used in one modification of the invention shown in its two positions;

FIGURE 5 is a schematic view of one of the modifications of the instant invention; and

FIGURE 6 is a schematic view of another modification.

BROAD DESCRIPTION OF FIGURES 1 AND 2 Referring to the drawings, wherein corresponding reference characters indicate corresponding parts throughout the several views of the drawings, numeral 1 designates an iron according to the invention. The iron 1 has a sole plate 2 and a heel section 4. The iron is seen resting on the sole or in its ironing position in FIGURE 1 and in its upright or resting position in FIGURE 2. In FIGURE 2 the iron rests on heel 4 and a rear portion 6 of a handle 8.

The iron disclosed is a conventional steam and dry iron having an electrical cord 10 connected to a conventional heating load and thermostat in the sole plate (not shown). Connected to the thermostat in the usual manner is a temperature regulating control operator 12. Also seen in FIGURES l and 2 is a conventional steam operating button 14. Located in the rear portion 6 of handle 8 is a switch operating button 16 which will be discussed more fully in connection with the various species disclosed.

DASH-POT OPERATED TIME DELAY CUT-OFF OF FIGURES 3 AND 4 Referencefwill now be made to the switch of FIG- URES 3 and 4 wherein button 16 is located in a switch housing 20 which is easily and conveniently placed in the rearward recessed portion of handle 8. Within button 16 is a time delay means illustrated as a dash-pot 22. The dash-pot has two chambers 24 and 26 separated by a piston member 28. The piston 28 is held stationary relative to housing 20 by means of a rod 30 anchored to the housing at 32. The button 16 is urged outwardly by a spring 34. Located on the piston 28 is a relatively small opening 36 and a much larger opening 38. Connected on side of chamber 26 is a flap valve 40.

Also located within housing 20 is a switch schematically represented by contacts 42 and 44. Contact 44 is fixedly mounted in the switch housing, and contact 42 is resiliently mounted on arm 46. Extending outwardly past the contacts is a portion 48 which is adapted to engage the button 16 when it has been completely depressed. Contacts 42 and 44 are connected to a pair of terminals 50 by wires 52. In Ser. No. 501,942 the entire switch is connected in series with the heating load and thermostat in the iron. In the instant invention the switch may e connected to the gate of a bidirectional semiconductive device as discussed below.

OPERATION OF FIGURES 3 AND 4 In operation, when the iron is in the position of FIG- URE l, the button 16 is in its outward position (FIGURE 3). However, when the iron is placed on its heel, the button 16 is gradually depressed against spring 34 forcing fluid slowly from chamber 26 through opening 36 into chamber 24. The flap valve 38, 40 is forced into the closed position. As this occurs, the button slowly moves toward extension 48 of switch arm 46. After a preselected time delay, determined by the size of opening 36 and the travel distance to extension 48, the switch contacts 42, 44 open and the circuit to the iron is broken.

When the iron is picked up, the spring pushes the button immediately outward forcing fluid through both openings 36 and 38. As noted above, the flap 40 will close the opening 38 during inward movement of the button, and it will be forced open during outward movement. Therefore, current will be cut-off a preselected period of time after the button is depressed and quickly restored when button is released.

TRIAC MODIFICATION OF FIGURE As seen in FIGURE 5 a pair of wires 100 and 102 lead into the electric iron having a heating element 104 of the conventional type connected in series therewith. Also connected in series with the heating element is a bidirectional semiconductive element such as a triode element or triac 106. The triac 106 has a pair of electrodes 108 and 110. The electrode 108 is connected in a line 112 to the load 104. The other electrode 110 is connected to the incoming wire 102. A gate 114 is connected to line 102 at a junction 116. The gate circuit includes a limiting resistance 118 and the normally closed switch of FIGURES 3 and 4. This switch is indicated schematically as 120. As seen in FIGURE 5 the switch may have the two contacts 42 and 44 shown in the preceding mentioned figures. Of course, any suitable type of time delay switch could be used. For example, a time delay mercury switch similar to that shown in FIGURE 2A of Ser. No. 501,942.

OPERATION OF FIGURE 5 When the iron 1 is in the position shown in FIGURE 1, switch 120 having contacts 42 and 44 are closed in the fashion seen in FIGURE 3. Therefore, with the iron plugged-in current will flow through line 102 to the junction 116. It will then flow through the limiting resistance 118 and the closed switch 120 to the gate of triac 106. Therefore, current will flow from line 102 through the electrodes and 108 of the triac to the heating element 104 of the iron and back through the line 100. When the iron is placed on its heel as seen in FIGURE 2 the normally closed switch will eventually open after the appropriate time delay as seen in FIGURE 4. This will cutoff the current to the gate 114 and the triac 106 will thus become non-conducting. Therefore, there will be no current flowing to the heating element of the iron.

TRIAC MODIFICATION OF FIGURE 6 The modification seen in FIGURE 6 is essentially the same as that shown in FIGURE 5, and therefore like elements have the same reference numerals. However, instead of the normally closed switch 120 in the gate circuit, a conventional normally open switch having a bridging member 132 across contacts 134 and 136 is connected between the gate and one side of the triac 106. This is connected to line 12 at the terminal 138.

OPERATION OF FIGURE 6 In the modification of FIGURE 6 when the iron is located in its operating position as seen in FIGURE 1, a switch such as that seen in FIGURE 3 holds a suitable switch in the open position. This is opposed to the closed position as seen in FIGURE 3. Therefore, current will flow through line 102 to the terminal 116. It will then flow through the limiting resistance 118 to the gate 114. This will energize the triac and current will flow from line 102 through the electrodes 110 and 108, line 112 to the heating element 104 and return to line 100.

When the iron is placed on its heel as seen in FIGURE 2, the normally open switch will slowly close by means of a suitable time delay means. Rather than the switch of FIGURE 4 being opened, the time delay element will cause the switch contacts to close. Therefore, the current will flow through the terminal 116, limiting resistance 118 and switch 134 to short-out or de-energize the triac 106. This will of course de-energize the heating element 104 and the iron will therefore be turned-0E.

While the invention has been described, it will be understood that it is capable of further modifications and this application is intended to cover any variations, uses, or adaptations of the invention following in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains, and as may be applied to the essential features hereinbefore set forth and as fall within the scope of the invention or the limits of the appended claims.

What is claimed is:

1. An electric iron comprising:

(a) a sole plate, a handle and a heel section,

(b) a heating load adjacent said sole plate,

(c) circuit means for connecting said heating load to a source of electrical potential,

(d) a bidirectional semiconductive element in said circuit, said element being in a normally conductive state,

(e) time delay means which is responsive to the placement of the iron in its rest position for rendering said bidirectional semiconductive element nonconductive a particular period of time after said iron is placed in its rest position, and

(f) means engageable with a support surface which when so engaged initiates operation of said time delay means.

2. An electric iron as defined in claim 1 wherein said time delay means is initiated when said iron is rested on said heel and handle.

3. An electric iron as defined in claim 1 wherein said element includes a pair of electrodes connected in series with said load and a control gate for energizing said element.

4. An electric iron as defined in claim 2 including a time delay switch in the control gate circuit.

5. An electric iron as defined in claim 1 wherein said element includes a control gate connected to said source of electrical potential, means for connecting said control gate to one electrode of said element.

6. An electric iron as defined in claim 5 including a normally open switch connected between said gate and one of said electrodes.

7. An electric iron as defined in claim 5 including a normally closed switch connected in series with said gate.

References Cited UNITED STATES PATENTS 2,382,587 8/1945 Thomas 219-257 2,833,903 5/1958 Waddell 219-251 3,385,957 5/1968 Munson et al 21950l OTHER REFERENCES General Electric Application Note, No. 22.35; May 1964; Triac Control for AC Power, by E. K. Howell, pages 3 and 4.

General Electric Seminar Application Information No. 671.1; March 1965; Economy Power Semiconductor Applications by Gutzwiller and Howell, page 6.

General Electric Applications, Note No. 200.35; March 1966; Using the Triac for Control of AC Power, by Galloway, pages 4-6.

JOSEPH V. TRUHE, Primary Examiner P. W. GOWDEY, Assistant Examiner 

